The present invention relates to a communication system and, more particularly, to a system for transmitting data between a transmitting platform and a receiving platform using a phased array antenna as the transmitting antenna located on the transmitting platform.
For cross-reference purposes, the existence of two filed applications are noted. The first application is Ser. No. 07/316,991, which ultimately became U.S. Pat. No. 5,157,393, entitled "Communication System for Transmitting Data Between a Transmitting Antenna Utilizing Leaky Coaxial Cable and a Receive Antenna in Relative Movement to One Another," by Timothy R. Fox and Jerry C. Posluszny. The second application is Ser. No. 07/317,026, now U.S. Pat. No. 5,140,696, entitled "Communication System for Transmitting Data Between A Transmitting Antenna Utilizing Strip-Line Transmission Line and a Receive Antenna in Relative Movement to One Another," by Timothy R. Fox. These applications and the present application are commonly owned by the same Assignee.
A communication system for transmitting data between a rotating platform and a stationary platform finds particular utility in CT scanners. The data come from a transmitter source and are applied to a suitable modulator that modulates a sinusoidal radio-frequency carrier signal. The modulated carrier signal is applied to the feedpoint of the transmitting antenna. The transmitter carrier source, the suitable modulator and the transmitting antenna are mounted on the transmitting platform, and the transmitting platform is rotating.
The transmission often is achieved using brushes sliding against slip rings to make a set of electrical connections between the rotating and stationary platforms. This mechanical contact causes a number of problems, however. One problem is that the mechanical interface is highly susceptible to wear. A second problem is that the mechanical interface achieves only an intermittent electrical contact.
Another problem with present CT scanners is that a large portion of the equipment rotates, but the data received from the rotating equipment must be communicated to a computer that does not rotate. Aside from the mechanical linkages discussed above, other CT scanners use flexible cables to connect the rotating platform to the fixed platform. As a result, most present CT scanners cannot allow the platform to rotate continuously. Thus, the rotating platform will make, for example, two rotations and then the transmitting cable must be rewound and the rotation started over again for another two rotations. This procedure causes wear on, and early destruction of the cables. Moreover, the scanning procedure is rendered unnecessarily long because the platform cannot continuously rotate.